Scale up point use step / 2 as initial coordinate, which is more symetric and…

Scale up point use step / 2 as initial coordinate, which is more symetric and matches ffmpeg exactly.
BUG=232
TEST=convert.exe -f 0 faces_352x288_P420.yuv faces_640x480_P420.yuv
R=ryanpetrie@google.com

Review URL: https://webrtc-codereview.appspot.com/1580005

git-svn-id: http://libyuv.googlecode.com/svn/trunk@706 16f28f9a-4ce2-e073-06de-1de4eb20be90

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 705
+Version: 706
 License: BSD
 License File: LICENSE
 

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_  // NOLINT
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 705
+#define LIBYUV_VERSION 706
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

source/scale.cc

@@ -3232,20 +3232,14 @@ static void ScalePlaneSimple(int src_width, int src_height,
                              const uint8* src_ptr, uint8* dst_ptr) {
   int dx = (Abs(src_width) << 16) / dst_width;
   int dy = (src_height << 16) / dst_height;
-  int x = 0;
-  int y = 0;
-  if (dst_width <= Abs(src_width)) {
-    x = (dx >> 1) - 32768;
-  }
+  int x = (dx >= 65536) ? ((dx >> 1) - 32768) : (dx >> 1);
+  int y = (dy >= 65536) ? ((dy >> 1) - 32768) : (dy >> 1);
   // Negative src_width means horizontally mirror.
   if (src_width < 0) {
     x += (dst_width - 1) * dx;
     dx = -dx;
     src_width = -src_width;
   }
-  if (dst_height <= src_height) {
-    y = (dy >> 1) - 32768;
-  }
 
   for (int j = 0; j < dst_height; ++j) {
     int xs = x;

source/scale_argb.cc

@@ -1081,12 +1081,8 @@ static void ScaleARGB(const uint8* src, int src_stride,
     // Scale step for point sampling duplicates all pixels equally.
     dx = (Abs(src_width) << 16) / dst_width;
     dy = (src_height << 16) / dst_height;
-    if (dst_width <= Abs(src_width)) {
-      x = (dx >> 1) - 32768;
-    }
-    if (dst_height <= src_height) {
-      y = (dy >> 1) - 32768;
-    }
+    x = (dx >= 65536) ? ((dx >> 1) - 32768) : (dx >> 1);
+    y = (dy >= 65536) ? ((dy >> 1) - 32768) : (dy >> 1);
   }
   // Negative src_width means horizontally mirror.
   if (src_width < 0) {